离子液体/多壁碳纳米管/壳聚糖修饰电极同时检测多巴胺、抗坏血酸及尿酸的研究

将水溶性离子液体([ BMIM] N(CN)2)、多壁碳纳米管(MWCNTs)和壳聚糖(CS)三者结合,修饰在玻碳电极上制备MWCNTs - IL - CS修饰玻碳电极,并研究了多巴胺(DA)、抗坏血酸(AA)、尿酸(UA)在该修饰电极上的电化学行为.扫描电子显微镜图显示,MWCNTs在IL - CS中能良好分散,并形...     

聚磺基水杨酸/碳纳米管修饰电极在抗坏血酸共存时测定多巴胺

研究了聚磺基水杨酸/多壁碳纳米管修饰玻碳电极的制备及多巴胺在此修饰电极上的电化学行为, 讨论了修饰条件、扫速、溶液 pH 以及抗坏血酸的干扰对多巴胺在这种复合物电极上响应的影响. 在 pH 7.4 磷酸盐缓冲溶液中, 在1.0×10-3 mol/L 抗坏血酸共存的条件下, 多巴胺氧化峰电流与其浓度在 5×10-7～10-4 mol/L 范围内分段呈线性关系, 检出限为 1.0×10-7 mol/L. 结果表明: 聚磺基水杨酸/多壁碳纳米管修饰电极结合了多壁碳纳米管灵敏度高和聚磺基水杨酸选择性好的优点, 可用于抗坏血酸共存条件下多巴胺的测定.     

β环糊精-碳纳米管/壳聚糖自组装膜修饰电极在过量抗坏血酸存在下测定多巴胺

基于β环糊精和碳纳米管可通过范德华力形成复合物, 利用壳聚糖分子以静电引力吸附富集碳纳米管-β环糊精, 采用层层自组装制备了β环糊精-碳纳米管/壳聚糖玻碳修饰电极, 并研究了多巴胺在修饰电极上的电化学行为. 在抗坏血酸和多巴胺共存体系中, 二者的氧化峰电位相差约163 mV, 据此建立了多巴胺的电化学选择性测定, 峰电流与浓度在1.0×10-6～7.0×10-5 mol/L 范围内呈良好的线性关系, 检出限为0.3 μmol/L.     

应用单壁碳纳米管修饰纳米碳纤维电极同时测定多巴胺和抗坏血酸

采用滴涂法制备了单壁碳纳米管修饰的纳米碳纤维电极,研究了多巴胺(DA)、抗坏血酸(AA)及其混合溶液在修饰前后电极上的电化学行为。在20 mmol/L Tris-HCl(pH 7.4)缓冲溶液中,修饰电极对DA和AA具有很好的电催化作用。采用差示脉冲伏安法对DA与AA混合溶液氧化峰电流与浓度的关系进行定量分析,DA和AA的氧化峰电流在1.0×10-7~5.0×10-5mol/L和1.0×10-5~1.0×10-3mol/L范围内与浓度呈线性关系,其线性回归方程及相关系数分别为Ip=0.0012c+4×10-9,r=0.9907;Ip=10-5c+7×10-10,r=0.9974,两种物质的检测限分别达到8.0×10-9mol/L和2×10-6mol/L。     

聚茜素红功能化碳纳米管修饰电极对多巴胺和抗坏血酸的电化学研究

采用电聚合方法将茜素红非共价修饰到碳纳米管上,制备了聚茜素红/碳纳米管修饰电极.以多巴胺(DA)和抗坏血酸(AA)为模型化合物,研究该修饰电极的电催化作用.结果表明:电聚合法使茜素红牢固地修饰到碳纳米管上,能显著提高电极的灵敏度和分子识别性能.DA和AA的氧化峰位分离达240 mV.在AA的存在下,DA的差分脉冲伏安法峰电流在1×10-7～1×10-5 mol/L范围内呈良好的线性关系,检测下限达1×10-7 mol/L.     

Nation-离子液体-碳纳米管复合膜修饰电极的制备及用于抗坏血酸、多巴胺及尿酸的同时测定

制备了一种新颖的Nation-离子液体一多壁碳纳米管复合膜修饰电极,并研究了抗坏血酸（AA）、多巴胺（DA）和尿酸（uA）在该修饰电极上的电化学行为．该修饰电极结合了多壁碳纳米管良好的导电性、离子液体优良的催化性能及Nation的高选择性等优点,对AA、DA和UA的氧化具有很好的催化和分离效果,实现了AA、DA和UA的同时测定．在三者共存体系中,AA和DA、DA和UA的氧化峰电位差分别为148和167mV．对AA、DA和UA的同时检测,线性范围分别为5-3200、1～1100和1-300gmol／L,检出限分别为1．66、0．33和0．33gmol／L．该修饰电极选择性好、稳定性高、重现性好,有望用于实际样品中AA、DA和UA的同时检测．     

聚合离子液体-多壁碳纳米管化学修饰电极同时测定多巴胺、抗坏血酸与尿酸

以1-乙烯基咪唑(1-Vinylimidazole)和1-溴乙烷(1-Bromoethane)为原料设计合成了溴化1-乙烯基-3-乙基咪唑功能化离子液体(1-Vinyl-3-ethylimidazolium bromide),以偶氮二异丁腈(Azobis(2-methylpropionitrile))为引发剂,制备了聚1-乙烯-3-乙基咪唑溴代盐聚合离子液体(Poly(ViEtIm~+Br~-))。在此基础上,利用Poly(ViEtIm~+Br~-)中咪唑基团与多壁碳纳米管之间的强π-π相互作用,在温和条件下,使用非共轭方法制备了聚合离子液体-多壁碳纳米管复合物修饰电极(Poly(ViEtIm~+Br~-)/MWCNTs/GCE),并成功应用于多巴胺(DA)、抗坏血酸(UA)和尿酸(UA)的同时测定。结果表明,在DA、AA、UA 3者的同时存在下,Poly(ViEtIm~+Br~-)/MWCNTs对3者的检测范围分别为2～180μmol/L、50～5 000μmol/L、4～50μmol/L,对应检出限分别为0.4、22.2、0.9μmol/L。将该电极用于维生素C注射剂中抗坏血酸浓度的检测以及盐酸多巴胺注射剂中多巴胺浓度的检测,回收率为98.8%～101%,检测效果良好。     

碳纳米管修饰电极对多巴胺和抗坏血酸的电催化氧化

研究了碳纳米管修饰玻碳电极 (NTCME)的制备方法及对多巴胺 (DA)和抗坏血酸 (AA)的电催化氧化作用。在磷酸盐缓冲溶液 (PBSpH 7.4)中 ,以NTCME为工作电极时 ,DA与AA的氧化电位分别为 0 .2 6和 0 .0 1V(vs.SCE) ,比在裸玻碳电极 (GC)上分别降低了 0 .0 7和 0 .6 2V。NTCME能消除DA与AA共存时测定的相互干扰。利用二阶导数卷积伏安法测定 ,DA与AA分别在 2 .0 0× 10 - 6～ 3.84× 10 - 4 和 7.99× 10 - 5～ 3.6 6× 10 - 3 mol L浓度范围内 ,峰高与浓度呈线性关系 ;检出限分别为 1.90× 10 - 7和 5 .96× 10 - 5mol L。     

多壁碳纳米管-Nafion化学修饰电极在高浓度抗坏血酸和尿酸体系中选择性测定多巴胺

多巴胺是人体内一种重要的神经传递物质 ,它参与许多生命过程[1] .因此 ,测定体内多巴胺的浓度十分重要 .多巴胺的电化学分析方法已有不少报道 [2 ,3 ] .然而 ,共存的抗坏血酸和尿酸的电化学性质与多巴胺相似 ,对多巴胺的测定会产生严重干扰 .因此建立一种选择性测定多巴胺的高灵敏度的分析方法就显得尤为重要 .碳纳米管是一种新型的纳米材料 [4 ] ,它的出现引起了广泛的研究兴趣 [5,6] .由于其性质稳定 ,不溶于水及一般的有机溶剂 ,因此限制了其在电分析方面的应用 .本文将多壁碳纳米管分散在 Nafion的无水乙醇中 ,得到了一种均匀的多壁碳…     

聚多巴胺/多壁碳纳米管/玻璃碳电极上多巴胺的电分析

基于多巴胺（DA）在多壁碳纳米管（MWCNTs）修饰玻璃碳（GC）电极上的电聚合,制得聚多巴胺(PDA)/MWCNTs/GC电极,并对该修饰电极进行了电化学阻抗谱 (EIS)和循环伏安法(CV)表征。 在该修饰电极上,DA呈现良好的电化学行为。在pH=7.4磷酸缓冲溶液中其氧化电流显著高于在裸电极上的响应,且能有效地抑制2.0 mmol/L抗坏血酸(AA)或K4Fe(CN)6的直接电化学响应,表明MWCNTs可增敏信号,且阳离子选择透过性PDA膜可抑制阴离子的电化学干扰。 采用CV实验检测DA,DA氧化的半微分伏安峰高(ipa-sd)与多巴胺浓度在0.08～1.76 μmol/L范围内呈线性关系,在无抗坏血酸和有0.5 mmol/L抗坏血酸共存时的线性回归方程分别为ipa-sd(μA/s1/2)=0.107+0.405c(μmol/L)（r2=0.986）和ipa-sd(μA/s1/2)=0.628+0.649c(μmol/L)(r2=0.992),检测限均为8.0×10-8 mol/L(S/N=3)。 该法用于盐酸多巴胺注射液中多巴胺的快速测定,结果满意。     

多壁碳纳米管修饰碳黑微电极同时测定多巴胺和抗坏血酸

制备了多壁碳纳米管修饰碳黑微电极,研究了多巴胺(DA)和抗坏血酸(AA)在该修饰电极上的电化学行为.实验表明,在pH 7.0的PBS缓冲溶液中,该修饰电极对DA和从均具有显著的催化氧化作用,AA与DA的氧化电位分别为30 mV和280 mV(vs.SCE).利用二次导数线性扫描伏安法测定,DA与AA的线性范围分别为6.0×10-9～2.0×10-4 mol/L和2.0×10-7～1.0×10-3mol/L,检出限为2.0×10-9mol/L 和1.0×10-7mol/L.方法已用于人工合成样品的分析.     

Simultaneous electrochemical sensing of ascorbic acid,dopamine and uric acid at anodized nanocrystalline graphite-like pyrolytic carbon film electrode

Nanocrystalline graphite-like pyrolytic carbon film (PCF) electrode fabricated by a non-catalytic chemical vapor deposition (CVD) process was used for the simultaneous electrochemical sensing of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The electrode was studied with respect to changes in electrocatalytic activity caused by a simple and fast electrochemical pretreatment. The anodized electrode exhibited excellent performance compared to many chemically modified electrodes in terms of detection limit, linear dynamic range, and sensitivity. Differential pulse voltammetry (DPV) was used for the simultaneous determination of ternary mixtures of DA, AA, and UA. Under optimum conditions, the detection limits were 2.9 μM for AA, 0.04 μM for DA, and 0.03 μM for UA with sensitivities of 0.078, 5.345, and 6.192 A M⁻¹, respectively. The peak separation was 219 mV between AA and DA and 150 mV between DA and UA. No electrode fouling was observed and good reproducibility was obtained in all the experiments. The sensor was successfully applied for the assay of DA in an injectable drug and UA in human urine by using standard addition method.     

Simultaneous voltammetric measurement of ascorbic acid and dopamine on poly(caffeic acid)-modified glassy carbon electrode

A poly(caffeic acid) thin film was deposited on the surface of a glassy carbon electrode by potentiostatic technique in an aqueous solution containing caffeic acid. The poly(caffeic acid)-modified electrode was used for the determination of ascorbic acid (AA), dopamine (DA), and their mixture by cyclic voltammetry. This modified electrode exhibited a potent and persistent electron-mediating behavior followed by well-separated oxidation peaks toward AA and DA at a scan rate of 10 mV s⁻¹ with a potential difference of 135 mV, which was large enough to determine AA and DA individually and simultaneously. The catalytic peak current obtained was linearly dependent on the AA and DA concentrations in the range of 2.0 × 10⁻⁵−1.2 × 10⁻³ and 1.0 × 10⁻⁶−4.0 × 10⁻⁵ mol L⁻¹ in 0.15 mol L⁻¹ phosphate buffer (pH 6.64). The detection limits for AA and DA were 9.0 × 10⁻⁶ and 4.0 × 10⁻⁷ mol L⁻¹, respectively. The modified electrode shows good sensitivity, selectivity, and stability and has been applied to the determination of DA and AA in real samples with satisfactory results.     

Simultaneous determination of acetaminophen,dopamine and ascorbic acid using a PbS nanoparticles Schiff base-modified carbon paste electrode

A highly sensitive method was investigated for the simultaneous determination of acetaminophen (AC), dopamine (DA), and ascorbic acid (AA) using a PbS nanoparticles Schiff base-modified carbon paste electrode (PSNSB/CPE). Differential pulse voltammetry peak currents of AC, DA and AA increased linearly with their concentrations within the ranges of 3.30 × 10⁻⁸–1.58 × 10⁻⁴ M, 5.0 × 10⁻⁸–1.2 × 10⁻⁴ M and 2.50 × 10⁻⁶–1.05 × 10⁻³ M, respectively, and the detection limits for AC, DA and AA were 5.36 × 10⁻⁹, 2.45 × 10⁻⁹ and 1.86 × 10⁻⁸ M, respectively. The peak potentials recorded in a phosphate buffer solution (PBS) of pH 4.6 were 0.672, 0.390, and 0.168 V (vs Ag/AgCl) for AC, DA and AA, respectively. The modified electrode was used for the determination of AC, DA, and AA simultaneously in real and synthetic samples.     

Simultaneous determination of ascorbic acid,dopamine and uric acid based on tryptophan functionalized graphene

A new type of tryptophan-functionalized graphene nanocomposite (Trp-GR) was synthesized by utilizing a facile ultrasonic method via π–π conjugate action between graphene (GR) and tryptophan (Trp) molecule. The material as prepared had well dispersivity in water and better conductivity than pure GR. The surface morphology of Trp-GR was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. The electrochemical behaviors of ascorbic acid (AA), dopamine (DA), and uric acid (UA) were investigated by cyclic voltammetry (CV) on the surface of Trp-GR. The separation of the oxidation peak potentials for AA–DA, DA–UA and UA–AA was about 182 mV, 125 mV and 307 mV, which allowed simultaneously determining AA, DA, and UA. Differential pulse voltammetery (DPV) was used for the determination of AA, DA, and UA in their mixture. Under optimum conditions, the linear response ranges for the determination of AA, DA, and UA were 0.2–12.9 mM, 0.5–110 μM, and 10–1000 μM, with the detection limits (S/N = 3) of 10.09 μM, 0.29 μM and 1.24 μM, respectively. Furthermore, the modified electrode was investigated for real sample analysis.     

Simultaneous determination of ascorbic acid, dopamine, uric acid and xanthine using a nanostructured polymer film modified electrode

This paper describes the simultaneous determination of ascorbic acid (AA), dopamine (DA), uric acid (UA) and xanthine (XN) using an ultrathin electropolymerized film of 2-amino-1,3,4-thiadiazole (p-ATD) modified glassy carbon (GC) electrode in 0.20 M phosphate buffer solution (pH 5.0). Bare GC electrode failed to resolve the voltammetric signals of AA, DA, UA and XN in a mixture. On the other hand, the p-ATD modified electrode separated the voltammetric signals of AA, DA, UA and XN with potential differences of 110, 152 and 392 mV between AA-DA, DA-UA and UA-XN, respectively and also enhanced their oxidation peak currents. The modified electrode could sense 5 μM DA and 10 μM each UA and XN even in the presence of 200 μM AA. The oxidation currents were increased from 30 to 300 μM for AA, 5 to 50 μM for DA and 10 to 100 μM for each UA and XN, and the lowest detection limit was found to be 2.01, 0.33, 0.19 and 0.59 μM for AA, DA, UA and XN, respectively (S/N = 3). The practical application of the present modified electrode was demonstrated by the determination of AA, UA and XN in human urine samples.     

Modification of carbon paste with congo red supported on multi-walled carbon nanotube for voltammetric determination of uric acid in the presence of ascorbic acid

A chemically modified carbon-paste electrode (CPE) is prepared by incorporating congo red (CR) immobilized on multi-walled carbon nanotube (MWCNT). The results show that CR is effectively immobilized on the surface of MWCNT under the ultrasonic agitation in aqueous solution and further incorporating the nafion. The prepared electrode, due to the electrostatic repulsions between the CR and ascorbate anion, is capable to mask the response of the ascorbic acid (AA) completely and provide an effective method for the detection of minor amounts of uric acid (UA) in the presence of high concentrations of AA. On the other hand, an increase in the microscopic area of the electrode by addition of MWCNT together with the electrocatalytic activity caused to a significant enhancement in the voltammetric response to UA. Optimization of the amounts of composite modifier in the matrix of CPE is performed by cyclic and differential pulse voltammetric measurements. The modified electrode shows a linear response to UA in the range of 1.0 × 10⁻⁷–1.0 × 10⁻⁴ M with a detection limit of 1.0 × 10⁻⁸ M. The electrode exhibits excellent accuracies for the determination of UA in the presence of high concentrations of AA (a recovery of 97.6%). The response of the electrode toward sulfhydryl compounds such as cysteine, penicillamine, and glutathione is not considerable. This reveals a good selectivity for the voltammetric response toward UA. The effective electrocatalytic property, ability for masking the voltammetric responses of the other biologically reducing agents, ease of preparation, and surface regeneration by simple polishing together with high reproducibility and stability of the responses make the modified electrode suitable for the selective and sensitive voltammetric detection of sub-micromolar amounts of UA in clinical and pharmaceutical preparations.     

Simultaneous determination of ascorbic acid,dopamine, uric acid and tryptophan on gold nanoparticles/overoxidized-polyimidazole composite modified glassy carbon electrode

A novel electrode was developed through electrodepositing gold nanoparticles (GNPs) on overoxidized-polyimidazole (PImox) film modified glassy carbon electrode (GCE). The combination of GNPs and the PImox film endowed the GNPs/PImox/GCE with good biological compatibility, high selectivity and sensitivity and excellent electrochemical catalytic activities towards ascorbic acid (AA), dopamine (DA), uric acid (UA) and tryptophan (Trp). In the fourfold co-existence system, the peak separations between AA–DA, DA–UA and UA–Trp were large up to 186, 165 and 285 mV, respectively. The calibration curves for AA, DA and UA were obtained in the range of 210.0–1010.0 μM, 5.0–268.0 μM and 6.0–486.0 μM with detection limits (S/N = 3) of 2.0 μM, 0.08 μM and 0.5 μM, respectively. Two linear calibrations for Trp were obtained over ranges of 3.0–34.0 μM and 84.0–464.0 μM with detection limit (S/N = 3) of 0.7 μM. In addition, the modified electrode was applied to detect AA, DA, UA and Trp in samples using standard addition method with satisfactory results.     

A simple electroanalytical methodology for the simultaneous determination of dopamine,serotonin and ascorbic acid using an unmodified edge plane pyrolytic graphite electrode

A simple method using an unmodified edge plane pyrolytic graphite electrode (EPPGE) is reported for the simultaneous determination of dopamine (DA), serotonin (ST) and ascorbic acid (AA). The performance of this electrode is superior to other unmodified carbon-based electrodes and also to many modified electrodes in terms of detection limit, sensitivity and peak separation for determination of DA, ST and AA. Using this method, detection limits of 90 nM, 60 nM and 200 nM were obtained for DA, ST and AA respectively. No electrode fouling is observed during a set of experiments and good sensitivity is obtained for the simultaneous determination of DA, ST and AA. The peaks for the three species are well resolved from each other and the electrode is successfully utilised for their determination in standard and real samples.